Lithium Metal Phosphate Cathode Crystallite Sizing for Low-Temperature Power
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Solution Overview
Problem
Lithium secondary batteries face challenges with low-temperature performance due to low ionic conductivity of lithium metal phosphate, which affects their capacity and energy density.
Innovation Solution
A cathode active material with lithium metal phosphate particles having crystallite sizes in the range of 150 nm to 450 nm in the (020) crystallographic plane direction, optimized through XRD analysis, is used to enhance ion diffusion and structural stability, potentially combined with a carbon coating for improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If lithium metal phosphate particles with larger crystallite size are used, then structural stability is improved, but ionic conductivity and low-temperature performance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystallite size of lithium metal phosphate particles within the range of 150-450 nm. This specific size range optimizes the balance between ionic conductivity (improved by smaller sizes) and structural stability (improved by larger sizes), while also enhancing low-temperature discharge capacity. The crystallite size is controlled through calcination temperature and time parameters during synthesis.
2Reliability
If lithium metal phosphate particles with smaller crystallite size are used, then ionic conductivity is improved, but structural stability deteriorates
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal crystallite size range (150-450 nm) that balances ionic conductivity and structural stability. Particles smaller than 150 nm lack sufficient structural stability, while particles larger than 450 nm exhibit reduced ionic conductivity. The specified range achieves both improved low-temperature performance and adequate structural stability.
3Stability of the object's composition
If crystallite size is increased to improve structural stability, then power properties at low temperature deteriorate
Solution Approach 1:
The patent optimizes power properties by controlling crystallite size within 150-450 nm. This size range ensures sufficient surface area for rapid lithium ion diffusion (improving power properties) while maintaining adequate structural stability. The optimal balance is achieved through precise control of calcination parameters.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves power properties and energy density at low temperatures while maintaining structural stability and process efficiency, reducing side reactions and enhancing discharge capacity.
Implementation Method 1
the direction of the crystallographic plane (020) of the lithium metal phosphate particle is a direction in which lithium ions are diffused or transferred
Implementation Method 2
a crystallite size of the lithium metal phosphate particle in a direction of a crystallographic plane (020) measured by an X-ray diffraction (XRD) analysis
Implementation Method 3
measured by an X-ray diffraction (XRD) analysis
Data Source
AI summary
Cathode active materials for lithium secondary batteries and lithium secondary batteries including the cathode active materials are disclosed. In some implementations, a cathode active material for a lithium secondary battery includes a lithium metal phosphate particle having a crystallite size in a range from 150 nm to 450 nm in a direction of a crystallographic plane (020) as measured by an X-ray diffraction (XRD) analysis. In some implementations, a lithium secondary battery includes a cathode including a cathode active material layer that includes a cathode active material for a lithium secondary battery, and an anode facing the cathode. In some implementations, an electrode crystallite size ratio defined by Equation 4 is in a range from 0.5 to 0.9.